The invention generally relates to a system for cementing a liner of a subterranean well.
Liners are commonly used in subterranean wells. As the name implies, a liner lines a section of a well bore. Such liners typically xe2x80x9changxe2x80x9d from a parent casing and may be cemented in place to the casing to provide structural support to the well bore.
In a typical liner cementing application, the liner is first hung on the parent casing, and the cementing tool is thereafter lowered to the liner. Cement is then pumped through the cementing tool to the area between the liner and the well bore. To force the cement down into the particular space being cemented, a displacement fluid, such as water (for example), may be used. In this manner, at the surface of the well, a device called a dart may be placed between the displacement fluid and the cement to form a barrier to prevent mixing of the cement and the displacement fluid. The dart follows the displacement fluid/cement interface downhole as more displacement fluid is introduced from the surface of the well to push the cement into the region to be cemented.
When the dart approaches the bottom of the cementing tool, the dart may engage a wiper that is part of and located at the bottom of the cementing tool. The dart seals a central passageway of the wiper through which the cement passes and dislodges the wiper from the cementing tool, thereby forming a barrier that wipes cement from the interior surface of the liner.
Unfortunately, the conventional wiper for use in liner applications typically is located at the bottom of the cementing tool and thus, is contacted by surfaces of varying diameters as the cementing tool is lowered downhole. As a result, depending on the geometry of the well bore and well bore completion, the wiper may be broken off or damaged as the cementing tool is being run downhole.
Conventional wiper darts are also not adapted to efficiently seal on a wide range of tubing diameters. For instance, conventional wiper darts may not be adequate to efficiently seal on larger diameter tubing (such as 4xe2x80x3) as well as smaller diameter tubing (such as 1.75xe2x80x3). Many completions currently include such a range of tubing diameters.
In addition, conventional systems often leave plug-mounting hardware in place that reduces the liner drift diameter and may prevent the performance of subsequent operations, such as cement evaluation. Retrieval of such plug mounting hardware is often required prior to the performance of the subsequent operations.
Moreover, in some instances as shown in the case of FIG. 1, the typical liner cementing application would provide undesirable consequences. FIG. 1 shows a casing 6 of a multilateral well. The casing 6 may include a junction 5, a part of the casing 6 in which a main vertical well bore 7a transitions into lateral well bores, such as lateral well bores 7b and 7c that are depicted in FIG. 1. Before the lateral well bores 7b and 7c are drilled, the main well bore 7a is drilled, and the junction 5 is cemented in place. To accomplish this, a cementing tool (not shown) may be lowered downhole to deliver cement into the region of the well bore 7a that surrounds the junction 5.
After the junction 5 is cemented in place, the lateral well bores 7b and 7c are drilled. After each lateral well bore 7b, 7c is drilled, a liner 8 is hung from one of the legs of the junction 5 by a liner hanger 3. After the liner 8 is hung, the liner 8 is then cemented in place.
To cement the liner in place, a cementing tool is typically deployed to the liner 8, and cement is pumped into the area between the liner 8 and the well bore. As the cement fills up such area, the cement displaces a fluid which must find a return path uphole of the liner hanger 3. To enable such return path, an operator either runs the liner cementing operation with the packer 2 unset, or installs a through port collar on the liner top. In either case, the return path enables displaced fluid, cement, or other debris to pass into the interior of the junction 5, which is undesirable for a variety of reasons. One of these reasons is that it may be necessary to mill out such displaced fluid, cement, or other debris from the junction after the end of the cementing operation, which milling operation may harm the structural integrity of the junction.
Thus, there is a continuing need for an arrangement and/or technique that addresses one or more of the problems that are stated above.
In an embodiment of the invention, an apparatus that is usable with a subterranean well includes a liner and a wiper. The liner is to be cemented inside the well bore, and the wiper, in a first mode, is connected to the liner when the liner is run downhole. In a second mode, the wiper is released from its connection to the liner to respond to a cement flow.
Advantages and other features of the invention will become apparent from the following drawings, specification and claims.